A standard telephone installation in the United States includes at least a pair of copper wires contained in a cable that the telephone company installs in a home or business. Each copper wire is capable of carrying a much greater bandwidth than is required to carry voice conversations. For example, human voices, speaking in normal conversational tones, can be carried in a frequency range of 0 to 3400 Hz. As telephone wires typically have the potential to carry frequencies of up to several million Hertz, the unused portion of the bandwidth can be exploited to carry data (e.g., for Internet access). An asymmetrical digital subscriber line (ADSL) is a telephone line that can be used for simultaneous transmissions of both voice and data.
To install a standard telephone line in a home or business, a telephone cable is usually laid from the street to the house. A typical telephone cable contains at least four separate metal wires, each wire encased in a insulating material. The house or business telephone system is connected to the public switching telephone network (PSTN) through a network interface device (NID). The FCC currently mandates that the NID terminate with a modular receptacle jack, also known as an RJ connector, so that before making a service call, the home or business owner can determine where a telephone line problem originates by plugging a telephone directly into the NID. If the telephone works, the problem is located on the customer's side of the NID; otherwise, the problem is located on the telephone company's side of the NID.
Typically inside but sometimes outside the house the cable enters a junction box which typically is contained within or located adjacent to the housing containing the NID. Inside the junction box the cable is opened, the wires are separated from each other, and at least one pair of wires are connected to screws called lugs. Frequently home or business owners or vendors such as burglar alarm companies and satellite and cable TV companies will tap into a customer's telephone lines by attaching their own wires to the lugs in the junction box, or if there are already too many wires attached to the lugs, the third-party systems may be spliced into wires attached to the lugs.
If an ADSL is in use in the household or business, a low bandpass filter must be installed because transmission on the data portion of the bandwidth will interfere with the voice signals of the lines used for regular (voice) telephone calls. The low bandpass filter blocks all signals above a certain frequency on those lines that will be used for only telephone calls to prevent data signals from interfering with voice signals, causing static on the telephone line. Installation of this filter typically takes approximately 20 minutes because splicing is necessary and tends to be rather difficult because space in the junction box is limited and the junction box typically already contains a number of wires and lugs. Splicing is undesirable and is a potential source of static problems because during splicing, wires may be stripped of their insulating covering and twisted together. Sometimes the fragile wires are damaged, creating a “high open” which may cause static on the line. Also, because the wires are now exposed, corrosion of the wires is likely to occur over time.
Burglar alarm systems and cable television systems are typically wired to the lugs in the junction box. If these systems are wired to the lugs at a point before the filter, signals from the CATV or burglar alarm can interfere with the ADSL signals. Frequently, installers of burglar alarm systems and television systems are unaware of the presence of an ADSL. Wiring a CATV or burglar alarm system to a point before the filter can result in static on the ADSL, which can lead to interference with data transmission or to interruption of the connection. Such problems are difficult to find and correct because repair persons may be unaware of the installation of the burglar alarm or television system.
It would be advantageous to installers of such interfaces, and cost effective for subscribers of such services, if apparatus and methods existed whereby the installer could easily, quickly, and accurately install an ADSL filter at the subscriber's location. It would be desirable that such systems eliminate the need for splicing, and reduce the likelihood of erroneous installation of third-party systems. Thus there is a need in the art for an ADSL interface adapter according to the present invention.